Did you actually read this page? Later he says:
"Up until April 17, 1975, it was a gentle land of peaceful smiling people and after that some horrible holocaust took place."
Is he actually saying Cambodia was a gentle land of peaceful smiling people prior to April 17, 1975? No, he is being sarcastic, obviously.
If you read the whole page you can find out what he thinks. He was not a supporter of the KR, in fact, he didn't like them at all, but he thought, and still thinks, that the reporting of them was overblown. He wrote a book with Edward Herman called "After the Cataclysm" which included a long section on the reporting of Cambodia, especially how things with little or no evidence were printed once and then picked up and reprinted all over the place, often mischaracterized.
I see very little difference between the KR hysteria and the POW/MIA hysteria. They seem to be some kind of psychological outlets, sort of like the Dolchstosslegende after Germany's defeat in World War I (which probably had more basis). There's no there there, so obviously this fills some kind of psychological need in the US.
Lance